The present invention relates generally to dielectrics for integrated circuit devices, and in particular to the development of doped aluminum oxide dielectrics and devices containing such dielectrics.
To meet demands for faster processors and higher capacity memories, integrated circuit (IC) designers are focusing on decreasing the minimum feature size within integrated circuits. By minimizing the feature size within an integrated circuit, device density on an individual chip increases exponentially, as desired, enabling designers to meet the demands imposed on them. As modern silicon devices become smaller and the minimum feature size of CMOS (complementary metal oxide semiconductor) devices approaches and goes below the 0.1 xcexcm regime, very thin gate insulators of thickness less than 2 nm (20 xc3x85) will be required to keep the capacitance of the DRAM (dynamic random access memory) capacitor cell in the range of 30 fF. This capacitance value is generally required to provide immunity to radiation, soft errors and a nominal signal-to-noise ratio.
Silicon dioxide (SiO2), the most commonly used insulator, shows high leakage current density at thicknesses in the range of 20 nm due to band-to-band tunneling current or Fowler-Nordheim tunneling current. As a result, high-k dielectric films such as aluminum oxide (Al2O3), tantalum pentoxide (Ta2O5) and titanium dioxide (TiO2) have received considerable interest as gate insulators to replace silicon dioxide.
While aluminum oxide has shown considerable promise, its porous nature leads to drawbacks. It has been noted that aluminum oxide porosity is generally the result of an acicular crystalline structure and that some pores may extend through the entire thickness of an aluminum oxide layer having a thickness on the order of 100 nm. Studies have also shown that exposure to humid atmospheres and even normal atmospheric conditions leads to a build-up of water in the pores of aluminum oxide films. This water build-up results in a loss of dielectric properties. In particular, water build-up can lead to a decrease in breakdown voltage of several orders of magnitude.
For the reasons stated above, and for other reasons stated below that will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for alternative aluminum oxide structures and methods of their production.
Aluminum oxide has shown considerable promise as a dielectric material for integrated circuit devices. However, its porous nature leads to drawbacks, in that the pores can adsorb water, thus resulting in a detrimental impact on the dielectric properties of the aluminum oxide material. The various embodiments of the invention involve a porous aluminum oxide layer having dopant material embedded in its pores and subsequently converted to a dielectric form. The doped aluminum oxide layer is formed sequentially to facilitate formation of a high-purity aluminum oxide layer and subsequently sealing its pores to impede water adsorption. Doped aluminum oxide layers of various embodiments are especially suited for use as gate dielectric layers, intergate dielectric layers and capacitor dielectric layers in various integrated circuit devices.
For one embodiment, the invention provides a doped aluminum oxide layer. The doped aluminum oxide layer includes an aluminum oxide layer having pores on a surface and a dopant material filling the pores. The dopant material is silicon, zirconium, hafnium or titanium and is applied to the aluminum oxide layer subsequent to a formation of the aluminum oxide layer.
For another embodiment, the invention provides a doped aluminum oxide layer. The doped aluminum oxide layer includes an aluminum oxide layer having pores on a surface and voids below the surface. The doped aluminum oxide layer further includes a dopant material of silicon, zirconium, hafnium or titanium. The pores contain at least a portion of the dopant material, and the voids are free of the dopant material.
For yet another embodiment, the invention provides a dielectric layer. The dielectric layer includes an aluminum oxide layer having pores on a surface and a second dielectric material embedded in the pores of the aluminum oxide layer. The second dielectric material is formed of a dopant material of silicon, zirconium, hafnium or titanium. The dopant material is embedded in the pores of the aluminum oxide layer and subsequently converted to its dielectric form.
For still another embodiment, the invention provides a dielectric layer. The dielectric layer includes an aluminum oxide layer having pores on a surface and voids below the surface. The dielectric layer further includes a second dielectric material. The second dielectric material is formed by depositing a dopant material in the pores and treating the dopant material to convert it to its dielectric form. The pores contain at least a portion of the second dielectric material, while the voids are free of the second dielectric material.
For one embodiment, the invention provides a method of forming a dielectric layer. The method includes forming a porous aluminum oxide layer on a substrate and forming a dopant layer on the porous aluminum oxide layer. The dopant layer contains a dopant material of silicon, zirconium, hafnium or titanium. The method further includes converting the dopant material to a dielectric form. For a further embodiment, excess dopant material is removed from the surface of the aluminum oxide layer prior to converting the dopant material to its dielectric form.
Further embodiments of the invention include apparatus and methods of varying scope.